java - 如何在 fx :include? 中指定资源

Question

我正在尝试加载包含另一个 FXML 文件 (Test2.fxml) 的 FXML 文件 (Test1.fxml)。 包含的文件应该使用它自己的资源包 (test2.properties)，这是由 fx:include 标记内的“resources”属性指定的。

当我运行应用程序时，FXMLLoader 抛出 NullPointerException，由以下代码引起。

resources = ResourceBundle.getBundle(value, Locale.getDefault(),
FXMLLoader.this.resources.getClass().getClassLoader());

通过调试发现FXMLLoader.this.resources为null，导致NPE。起初我以为我只是提供了一个错误的文件路径，但请注意，这发生在 ResourceBundle 甚至尝试加载属性文件之前!

知道如何解决这个问题以便加载资源吗？

下面是我的文件。它们都在同一个目录中(为简单起见，默认包)。

TestApp.java

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class TestApp extends Application
{
    @Override
    public void start(Stage primaryStage) throws Exception
    {
        FXMLLoader loader = new FXMLLoader();
        loader.setLocation(getClass().getClassLoader().getResource("Test1.fxml"));
        loader.load();

        Scene scene = new Scene((Parent) loader.getRoot());
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void main(String[] args)
    {
        launch(args);
    }
}

Test1.fxml

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>

<BorderPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.40" xmlns:fx="http://javafx.com/fxml/1">
   <center>
      <fx:include source="Test2.fxml" resources="test2" />
   </center>
</BorderPane>

Test2.fxml

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>

<BorderPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.40" xmlns:fx="http://javafx.com/fxml/1">
   <center>
      <Label text="%test" BorderPane.alignment="CENTER" />
   </center>
</BorderPane>

test2.properties

test=Test 2

完整的堆栈跟踪:

Exception in Application start method
java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)
    at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.RuntimeException: Exception in Application start method
    at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$152(LauncherImpl.java:182)
    at com.sun.javafx.application.LauncherImpl$$Lambda$50/1645995473.run(Unknown Source)
    at java.lang.Thread.run(Thread.java:745)
Caused by: javafx.fxml.LoadException: 
/C:/Eclipse/fx/bin/Test1.fxml:9

    at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2605)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2583)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2445)
    at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2413)
    at TestApp.start(TestApp.java:16)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$159(LauncherImpl.java:863)
    at com.sun.javafx.application.LauncherImpl$$Lambda$53/1370226249.run(Unknown Source)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$172(PlatformImpl.java:326)
    at com.sun.javafx.application.PlatformImpl$$Lambda$45/186276003.run(Unknown Source)
    at com.sun.javafx.application.PlatformImpl.lambda$null$170(PlatformImpl.java:295)
    at com.sun.javafx.application.PlatformImpl$$Lambda$48/1026297962.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$171(PlatformImpl.java:294)
    at com.sun.javafx.application.PlatformImpl$$Lambda$47/237061348.run(Unknown Source)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$145(WinApplication.java:101)
    at com.sun.glass.ui.win.WinApplication$$Lambda$36/2117255219.run(Unknown Source)
    ... 1 more
Caused by: java.lang.NullPointerException
    at javafx.fxml.FXMLLoader$IncludeElement.processAttribute(FXMLLoader.java:1088)
    at javafx.fxml.FXMLLoader$Element.processStartElement(FXMLLoader.java:216)
    at javafx.fxml.FXMLLoader$ValueElement.processStartElement(FXMLLoader.java:740)
    at javafx.fxml.FXMLLoader.processStartElement(FXMLLoader.java:2711)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2531)
    ... 17 more
Exception running application TestApp

Answer 1

有一个bug在 FXMLLoader 中。要解决此错误:

1. 加载根 fxml 文件时，必须为 FXMLLoader 实例定义根 ResourceBundle。
2. 根资源包必须从另一个类加载器加载，然后是引导类加载器。

可以在 oracle 论坛中找到可能的解决方法:https://community.oracle.com/message/11240449

如果您不需要根 fxml 文件的 resourceBundle(如您的示例)，您可以使用这个简单的解决方法:

TestApp.java

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class TestApp extends Application
{
    @Override
    public void start(Stage primaryStage) throws Exception
    {
        FXMLLoader loader = new FXMLLoader();

        // add the resource wrapper
        loader.setResources(new ResourceWrapper());

        loader.setLocation(getClass().getClassLoader().getResource("Test1.fxml"));
        loader.load();

        Scene scene = new Scene((Parent) loader.getRoot());
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void main(String[] args)
    {
        launch(args);
    }

    // an empty resource bundle
    private static class ResourceWrapper extends ListResourceBundle {
        @Override
        protected Object[][] getContents() {
            return new Object[0][];
        }
    }
}